Method of, and apparatus for, dissolving crude oil sludge

ABSTRACT

The method includes the steps of pumping solvent under pressure into the mass of sludge, pumping the resultant mixture of solvent and dissolved sludge into the remaining mass of sludge until all or substantially all of the sludge is dissolved to a pumpable viscosity, pumping the dissolved sludge from the containment, and monitoring and controlling the aforementioned steps remotely. Apparatus for performing the method is also disclosed. This includes elements for pumping the solvent and dissolved sludge mixture into the remaining mass of sludge, elements for removing the dissolved sludge from the containment, elements for supporting and transporting the pumping elements through the dissolved sludge mixture and elements for monitoring and controlling the apparatus remotely.

This invention relates to a method of, and apparatus for, dissolvingcrude oil sludge held in containments such as bulk storage tanks ortankers or holes in the ground.

As crude oil becomes more viscous it can coalesce into what is generallyreferred to as sludge. The sludge represents value to its owner if itcan be dissolved and incorporated into the owner's income-earningactivities. Where sludge is contained in a receptacle such as a storageor settlement tank, the recovery of such sludge can be a hazardousoperation particularly if operatives are required to wear full breathingand safety equipment to be able to enter the tank in order to spraydissolving-fluid at the sludge. As man-way entry/exit points of storagetanks are of limited dimension the apparatus is capable of being packedin a foldaway form to facilitate egress through such entry/exit pointsand unfolded into its operating mode after entry into the area to beworked on.

Conventionally sludge is removed from tanks by a variety of methodswhich range from digging it out to pumping water or chemicals underpressure to create an emulsion which is then pumped out and disposed of.There are significant disadvantages to these methods which the presentinvention seeks to overcome. The disadvantages are health and safety,environmental and economic. Health and safety, because of the need foroperatives to work in tanks. Environmental because if the crude oilsludge cannot be recovered for use then it has to be disposed of in anenvironmentally friendly way. Economic because the sludge representsvalue if the value of the sludge can be released and also whilst thesludge is in the tank it takes up valuable space.

Further, in order to clean the inside of tanks for, say, inspection,repair or change of use cleaning devices, referred to as spinners, areused which, because of their method of construction, do not allow forthem to be operated at other than the speed designed by the factorysetting. That “one model fits all” approach has limitations as it meansthat the cleaning operation inputs—such as solvent or cleaning fluid andcleaning medium—and outputs—such as effluent—all have a cost which couldbe more easily controlled if the speed of operation could be accuratelytailored to the job. To overcome this disadvantage and to be able toobtain the desired economies in operation apparatus to be specified canbe deployed in such environments.

According to one aspect of the present invention there is provided amethod of dissolving crude oil sludge in a containment, comprising thesteps of:

-   -   a. pumping solvent under pressure into the mass of sludge.    -   b. pumping the resulting mixture of solvent and dissolved sludge        into the remaining mass of sludge until all or substantially all        of the sludge is dissolved to a pumpable viscosity,    -   c. pumping the dissolved sludge from the containment, and    -   d. monitoring and controlling the above steps remotely.

Preferred and/or optional features of the first aspect of the inventionare set out in claims 2 to 4.

According to another aspect of the present invention there is providedapparatus for performing the method according to the first aspect of theinvention, comprising means for pumping the solvent and dissolved sludgemixture into the remaining mass of sludge, means for removing thedissolved sludge from the containment, means for supporting andtransporting the pumping means through the dissolved sludge mixture andmeans for monitoring and controlling the apparatus remotely.

Preferred and/or optional features of said another aspect of theinvention are set out in claims 6 to 10.

The preferred solvent is formulated from derivatives of orange oils anda synthesized mineral oil, such as Pronatur Orange Solvent made by OrapiS.A. of 12 Rue Pierre Mendes, 69511 Vaulx en Velin, Cedex, Lyon, France.When this solvent is pumped into sludge the sludge appears to dissolveimmediately. The amount of solvent required depends on three factors,the pour-point temperature of the sludge, the % of wax contained in thesludge, and the maximum acceptable viscosity of dissolved sludge.

Preferably, the apparatus comprises a multi-nozzled rotor or spinner.The angle at which the nozzles are set can be varied in order to obtainoptimum working of a particular rotor or spinner in a particular tank.Also, preferably, there is provided a means of stopping the flow ofcleaning fluid through one or more nozzles in order to allow the samebasic rotor or spinner design to be usable in open-topped containers aswell as enclosed containers and to avoid drenching the apparatus underthe path of the jets of solvent or cleaning fluid which would otherwiseflow through the nozzles as the rotor or spinner rotates.

A preferred embodiment of the apparatus is summarized as a multi-nozzledrotor or spinner which is releasably secured to a pump and driven by aflow of solvent or solvent and dissolved sludge mixture or cleaningfluid pumped under pressure from the pump. The pump may be eitherreleasably secured to a raft, tractor or sump-cone lowered onto thefloor of the containment or as part of clean-in-place (CIP) setting tothe tank to be cleaned or external to the tank—depending oncircumstances applying at site of operation—so that the force of thesolvent or solvent and dissolving sludge mixture or cleaning fluiddelivered through outlet nozzles located at specific points and angleson, along or around the circumference of a rotor block or outlet pipesattached to the rotor block causes the rotor block to rotate in acontrolled manner. The provision of a releasably secured collar orshoulder within the rotor block enables the directional flow throughcertain nozzles to be restricted or stopped for operational needs, suchas being able to clean open-topped containers or to avoid drenching theapparatus under the path of the jets of solvent or cleaning fluid whichwould otherwise flow through the nozzles as the rotor or spinnerrotates. The solvent is used to dissolve the un-dissolved sludge itcomes into contact with and also causes the rotor or spinner to rotatein a controlled manner to increase the area of sludge to be dissolved.On a modified rotor block the rotor or spinner can be transformed into apaddle-wheel by the attachment of transverse flats to the rim of therotor block which when properly located on the raft and activated bysolenoid switches is used to assist propulsion of the raft through thedissolved sludge in addition to sludge pumped directly to create suchpropulsion. Lights and a CCTV camera releasably secured to the raft,tractor or sump-cone illuminate and survey the area of sludge beingdissolved and observe obstructions or other impediments to progress.Sensors may be provided for obtaining trigonometric readings topin-point the location of the raft in tank. The raft may have severalreleasably connected floats to provide buoyancy to support the weight ofthe equipment. The tractor may have wheels or caterpillar tracks poweredby an electric motor. A control box may be provided with appropriatesoftware and means of two-way electrical or electronic communicationwith the different pieces of equipment to control the operation of theapparatus and ancillary equipment and devices such as generators,compressors, pumps, CCTV recording and play-back equipment as may benecessary to support the use of the apparatus when in operatingconditions.

The invention will now be more particularly described, by way ofexample, with reference to the accompanying drawings in which:

FIG. 1 shows one embodiment of apparatus in operating mode when attachedto a raft.

FIG. 2 shows another embodiment according to the invention in operatingmode when attached to a tractor.

FIG. 3 shows yet another embodiment in operating mode when attached to asump-cone.

FIG. 4 shows the rotor block of the apparatus of FIGS. 1, 2 and 3.

FIG. 5 shows details of the spinner assembly of yet a further embodimentthe apparatus.

FIG. 6 shows a modification to threaded rotor/drive connection to createa “shoulder”.

FIG. 7 shows another modification to threaded rotor connection to createa “shoulder”.

Referring to the drawings the apparatus shown therein comprises buoyancyfloats 1 (FIG. 1) or a tractor 21 (FIG. 2) or a sump-cone 20 (FIG. 3), apump 2 connected by a flow-pipe 3 to a rotor comprising a rotor block 4and a plurality of radially outwardly extending arms 5 releasablyconnected to the rotor block 4, CCTV camera 22 and lights 6; allreleasably connected by, for example, flexible joints, circlips, unionsor similar means (not shown). At convenient points on the raft 1,tractor 21 or sump-cone 20, cleats or similar devices (not shown) arefitted to facilitate securing or manoeuvring the apparatus by ropes orsimilar means (not shown).

As shown in FIG. 4, the rotor block 4 is connected to the flow-pipe 3 byan inlet assembly 10 which comprises a threaded inlet nut 7, a threadedinlet-nut stop 8 and a threaded rotor connection 9, bearings 11supporting the rotor connection 9 on the inlet-nut stop 8, and seals 12.The threaded rotor connection 9 joins the inlet assembly 10 to the rotorblock 4 from which the arms 5 extend.

Each arm 5 carries one or preferably, as shown, a plurality of nozzles13. The nozzles 13 are inclined to the vertical in order to propel therotor when solvent is pumped through the arms 5 and the nozzles 13 bythe pump 2. The number of nozzles 13 or the position of the nozzles 13on the arms 5 or the angle of inclination of the nozzles 13 can bevaried to vary the speed of the rotation of the rotor and to provide aspray pattern which provides the greatest contact with the sludge to bedissolved.

FIG. 5 shows an alternative rotor (or spinner) comprising a disc-shapedrotor block 4 and a plurality of nozzles 13 circumferentially spacedapart on the block 4.

The nozzles 13 are releasably connected to the rotor block 4 by threadedconnections. This allows nozzles 13 with an appropriate orifice size tobe selected to accommodate a desired flow rate and to provide a desiredspeed of rotation. The number of nozzles 13 or the angle of inclinationof each nozzle 13 to a diametral plane through the rotor block 4 canalso be varied to vary the speed of rotation of the rotor. Each nozzlehas a cap 31 releasably attached to the rotor block 4 by a screw or bolt35. The rotor block 4 is supported by a mounting comprising an angleconnector 30 having an inlet and an outlet, an inlet assembly connectedto the inlet of the connector 30 and an outlet assembly connected to theoutlet of the connector 30. The inlet assembly comprises a collar 8threadably connected to the inlet of the connector 30, a rotor/driveconnection 9 which is threadably connected to a drive nut 7 and which isrotatably supported by bearings 11A mounted in the collar 8, seal 12A,washer 38 and locking nut 37. The outlet assembly comprises a collar 32threadably connected to the outlet of the connector 30, a rotorconnection 36 which is threadably connected to the rotor block 4 andwhich is rotatably supported by bearings 11B mounted in collar 32, seal12B, washer 38 and a locking nut 37. The rotor/drive connection 9includes a bevel gear 33 to mesh with a bevel gear 34 attached to therotor connection 36 to allow the rotary action of the rotor 4 to betransmitted to a different plane from the drive nut 7.

FIG. 6 shows a setting in which the rotor 4 is connected directly to thecollar 8 and the rotor/drive connection 9 is extended and profiled tocreate a shoulder 40 to allow one or more nozzles 13 to be closed offsequentially as the rotor 4 rotates.

FIG. 7 shows a setting in which the rotor 4 is connected directly to therotor connection 36 and the collar 32 is profiled to allow a shoulder 40to be releasably attached to allow one or more nozzles 13 to be closedoff sequentially as the rotor 4 rotates.

Controls 14 to stop/start and monitor operations are maintained outsidethe tank but releasably connected to the apparatus and other equipmentbeing used. The control box and associated software is typical of CIPcontrol equipment used in the dairy industry.

The method for using the apparatus will now be described envisaging

-   -   A. a circumstance in which buoyancy from a raft is desirable,    -   B. a circumstance in which the use of a tractor or similar means        of propulsion is desirable,    -   C. a circumstance in which a static location is desirable,    -   D. for cleaning the walls and bottom of an open-topped tank or        use as a paddle-wheel,    -   E. for cleaning all surfaces of an enclosed tank,    -   F. for cleaning either the bottoms of tanks or inside surface of        a pipeline.

In each case sufficient solvent will need to be pumped into the tank tocreate a pool of solvent and sludge in order to prime and operate thepump used with the apparatus. Thus, with circumstance A, after a pool ofdissolved sludge is created, the raft and attached apparatus as shown inFIG. 1 is placed in that pool; the pump 2 is then in a position to suckthe dissolved sludge in through inlet port 15 of the pump and force italong pipe 3 to the rotor block 4, along the spray arms 5 and outthrough the nozzles 13. The combined force and flow of solvent anddissolved sludge through the nozzles 13 causes more crude to dissolvethus increasing the size of the pool of dissolved sludge. As the poolsize increases the raft will need to be moved in order to maintaincontact with undissolved sludge. This movement is obtained from thethrust derived by diverting via valve 18 dissolved sludge from flow pipe3 along pipe 16 to an outlet port 17, at which port may be located arotor or spinner modified as a paddle-wheel to provide propulsion whenthe diverted sludge causes this paddle-wheel to rotate. The viscosity ofthe pool of dissolved sludge can be maintained by adding more solventusing an externally located pump (not shown) and by using an agitatingmechanism such as a slow-speed propeller (not shown) located in the poolto cause the dissolved sludge to circulate. When the pool of solvent hasreached the desired viscosity required by the owner—as measured byin-line Viscometer (not shown)—it can be removed either by pumping itdirectly from the tank, or indirectly by pumping sufficient water intothe tank to allow the oil to be floated out of the tank through outletports in the wall of the tank into appropriate recovery vessels. In theevent that the apparatus needs to be recovered, the raft 1 has ropesattached to cleats (not shown) and connected to a winch (not shown)located outside the tank in order to winch the raft and apparatus tosafety.

Whilst the apparatus is in operation the sludge being dissolved can beilluminated by lights 6 so that human operators located outside the tankcan observe the operations via the CCTV camera 22 connected to a monitorscreen (not shown) and control operations with the control box 14.

With circumstance B, after a pool of dissolved sludge is created, thetractor 21 and attached apparatus as shown in FIG. 2 is placed in thatpool; the pump 2 is then in a position to suck the dissolved sludge inthrough inlet port 15 and force it along pipe 3 to the rotor block 4along the spray arms 5 and out through the nozzles 13. The combinedforce and flow of solvent and dissolved sludge through the nozzles 13causes more crude to dissolve thus increasing the size of the pool ofdissolved sludge. As the pool size increases the apparatus will need tobe moved in order to maintain contact with undissolved sludge. Thismovement is obtained by using an electric-motor powered tractor 21 whichhas been approved for use in this environment. The viscosity of the poolof dissolved sludge can be maintained by adding more solvent using anexternally located pump (not shown) and by using an agitating mechanismsuch as a slow-speed propeller (not shown) located in the pool to causethe dissolved sludge to circulate. When the pool of solvent has reachedthe desired viscosity required by the owner—as measured by an in-lineViscometer (not shown)—it can be removed either by pumping it directlyfrom the tank, or indirectly by pumping sufficient water into the tankto allow the oil to be floated out of the tank through the outlet portsin the wall of the tank into appropriate recovery vessels. In the eventthat the apparatus needs to be recovered, the tractor 21 has ropesattached to cleats (not shown) and connected to a winch (not shown)located outside the tank in order to winch the tractor and apparatus tosafety.

Whilst the apparatus is in operation the sludge being dissolved can beilluminated by lights 6 so that human operators located outside the tankcan observe the operations via the CCTV camera 22 connected to a monitorscreen (not shown) and control operations with the control box 14.

With circumstance C, a pool of sludge needs to be created in a differentfashion where the sludge is of such a depth that entrance into the tankthrough a man-way in the side wall is not desirable or not possible andwhere entrance is only possible through the roof or floating membranecovering the sludge. In this case it may be first necessary to lowerthrough a man-way a sump-cone 20 as shown in FIG. 3 which, because ofits weight, will sink into the sludge and have the effect of allowing apool of solvent and solvent sludge mixture to accumulate in thesump-cone 20 in order that the pump 2 can operate. The sump-cone 20 issupported by legs 19 and is in the shape of an inverted truncated conewith means for lowering/lifting it (not shown) and releasably securing(not shown) the pump 2 inside the space contained by the skin of thecone. After a pool of solvent or dissolved sludge is created in thesump-cone 20, the pump 2 is then in a position to suck the dissolvedsludge in through inlet port 15 and force it along pipe 3 to the rotorblock 4 along the spray arms 5 and out through the nozzles 13. Thecombined force and flow of solvent and dissolved sludge through thenozzles 13 causes more crude to dissolve thus increasing the size of thepool of dissolved sludge. The viscosity of the pool of dissolved sludgecan be maintained by adding more solvent using an externally locatedpump (not shown) and by using an agitating mechanism such as aslow-speed propeller (not shown) located in the pool to cause thedissolved sludge to circulate. As the pool depth increases some of thedissolved sludge will need to be pumped out of the tank in order toallow the remaining sludge to settle into the space created. Thisprocess will then continue until such time that it is possible to deploythe apparatus attached to a raft 1 as described in Circumstance A. Whenthe pool of solvent has reached the desired viscosity required by theowner—as measured by an in-line Viscometer (not shown)—it can be removedeither by pumping it directly from the tank, or indirectly—when theside-wall man-ways are accessible—by pumping sufficient water into thetank to allow the oil to be floated out of the tank through such outletports in the wall of the tank into appropriate recovery vessels.

Whilst the apparatus is in operation the sludge being dissolved can beilluminated by lights 6 in order that human operators located outsidethe tank can observe the operations via the CCTV camera 22 connected toa monitor screen (not shown) and control operations with the control box14.

The raft 1 is conveniently assembled from connectable plastics or otherstrong light-weight materials to provide sufficient buoyancy for theweight of the raft and its equipment and capable of being easilyassembled after entry into and disassembled before egress fromstorage/settlement tank through a man-way. The tractor 21 is driven byan electric motor similar to tractors used in gas pipelines and as suchwarranted suitable for use in an explosive environment.

The pumping mechanism comprises pump 2 and rotor block 4 with spray arms5 or nozzles 13 through which the solvent and sludge mixture isdelivered and includes connecting pipework 3 and 16 and valve 18. Thepump 2 is of a type suitable for hazardous environments. The rotor block4 and the spray arms 5 have nozzles 13 to create flat jets so that asthe rotor block 4 rotates the kinetic energy derived from the force ofthe jets of solvent and solvent-sludge mixture delivered through thenozzles 13 accelerates the dissolution of the sludge. The pump 2operates at a convenient pressure up to 5 Bar and the nozzles 13 willaccommodate the flow rate delivered by the pump 2. Rotation of the rotorblock 4 is achieved by the flow of fluid through the nozzles 13 and thespeed of rotation is determined by the location of the nozzles 13.

The control and monitoring of the operations is achieved by mounting theCCTV camera 22 and lights 6 on the raft 1, tractor 21 or sump-cone 20and a control module 14 to stop or start the different functionsinvolved with pumping, moving, scanning, recording, locating, measuringis connected electronically to the apparatus but located outside thetank.

The apparatus described above can also be used to clean any residue andscale from the tank, after the sludge has been dissolved. In this case,a dilute acid solution is pumped through the apparatus by the pump 2.

With circumstance D to clean the walls and bottom of an open-topped tankor use as a paddle-wheel when transverse flats (not shown) have beenadded to the rim of the rotor block 4, the flow of fluid through some ofthe spray nozzles 13 will need to be stopped as the rotor block 4rotates. This is achieved by ensuring that a shoulder 40 of appropriatedimension is releasably attached to or formed as part of the collar 32and that the complete assembly is appropriately positioned in the tankto ensure the spray jet leaving spray nozzle 13 reaches the desiredheight up the wall of the tank. Thus, with a correctly positionedshoulder 40, fluid to nozzles 13 will be sequentially blocked as theoutlet to nozzle cap 31 passes behind shoulder 40. As rotor block 4rotates the flow through spray nozzle 13 is reinstated as the outlet tospray nozzle 13 clears shoulder 40. With more than one spray nozzle 13rotation of rotor block 4 can be maintained providing the force fromflow of fluid through unmasked spray nozzles 13 is sufficient toovercome the frictional resistance of the complete unit. The speed ofrotation is determined by the direction of the jet of cleaning fluidleaving spray nozzle 13. There is no rotation when nozzle 13, screw 35and centre point of rotor 4 are in a straight line (0 degrees). Therewill be maximum rotation if the nozzle cap 31 is turned 90 degrees. Anoperator can set his angle of deflection—rotating the nozzle cap31—between 0 degrees and 90 degrees to suit his operating requirementabove the frictional resistance of the complete unit.

With circumstance E, to clean all surfaces of an enclosed tank cleaningfluid will need to flow through all of the spray nozzles 13 as the rotorblock 4 rotates when rotor block 4 is attached to rotor connector 36.The speed of rotation is determined by the direction of the jet ofcleaning fluid leaving the spray nozzles 13. There will be no rotationwhen nozzle 13, screw 35 and centre point of rotor 4 lie in a commonplane (0 degrees). There will be maximum rotation if the nozzle cap 31is turned through 90 degrees. An operator can set his angle ofdeflection—rotating the nozzle cap 31—between 0 degrees and 90 degreesto suit his operating requirement above the frictional resistance of thecomplete unit.

With circumstance F, to clean the bottom of a tank or inside surface ofa pipeline cleaning fluid will need to flow through all of the spraynozzles 13 as the rotor block 4 rotates when rotor block 4 is attacheddirectly to collar 8. The speed of rotation is determined by thedirection of the jet of cleaning fluid leaving spray nozzle 13. There isno rotation when nozzle 13, screw 35 and centre point of rotor 4 are ina common plane (0 degrees). There will be maximum rotation if the nozzlecap 31 is turned through 90 degrees. An operator can set his angle ofdeflection—rotating the nozzle cap 31—between 0 degrees and 90 degreesto suit his operating requirement above the frictional resistance of thecomplete unit.

The oil contained in the dissolved sludge pumped from the tank asdescribed above is preferably recovered and incorporated in the owner'soil processing/trading activities.

The methods and apparatus described above are given by way of exampleonly and various modifications will be apparent to persons skilled inthe art without departing from the scope of the invention as defined bythe appended claims.

1. A method of dissolving crude oil sludge in a containment, comprisingthe steps of: a. pumping solvent under pressure into the mass of sludge,b pumping the resulting mixture of solvent and dissolved sludge into theremaining mass of sludge until all or substantially all of the sludge isdissolved to a pumpable viscosity, c. pumping the dissolved sludge fromthe containment, and d. monitoring and controlling the above stepsremotely.
 2. A method as claimed in claim 1, wherein step B. is carriedout on a continuous basis until all or substantially all of the sludgeis dissolved to a pumpable viscosity.
 3. A method as claimed in claim 1,wherein the oil in the dissolved sludge pumped from the containment isthen recovered.
 4. A method, as claimed in claim 1, comprising thefurther step of cleaning the containment by pumping a dilute acidsolution into the containment.
 5. A method as claimed in claim 1,wherein the solvent is formulated from derivatives of orange oils and asynthesised mineral oil.
 6. Apparatus for performing the method asclaimed in claim 1, comprising means for pumping the solvent anddissolved sludge mixture into the remaining mass of sludge, means forremoving the dissolved sludge from the containment, means for supportingand transporting the pumping means through the dissolved sludge mixtureand means for monitoring and controlling the apparatus remotely. 7.Apparatus as claimed in claim 6, wherein the means for pumping thesolvent and dissolved sludge mixture into the remaining mass of sludgecomprises a pump and a rotor having a plurality of outlet for nozzlesthrough which the solvent and dissolved sludge mixture are directed intothe remaining mass of sludge.
 8. Apparatus as claimed in claim 7,wherein the rotor has a plurality of angularly spaced arms each havingtwo or more nozzles.
 9. Apparatus as claimed in claim 7, wherein therotor is disc-shaped and has a plurality of circumferentially spacednozzles.
 10. Apparatus as claimed in claim 7, wherein means are providedfor sequentially restricting the flow through specific nozzles as therotor rotates to provide a desired spreading pattern.
 11. Apparatus asclaimed in claim 7, further comprising valve means between the pump andthe rotor to permit diversion of some of the flow in order to propel theapparatus through the dissolved sludge.
 12. A method as claimed in claim2, wherein the oil in the dissolved sludge pumped from the containmentis then recovered.
 13. A method, as claimed in claim 2, comprising thefurther step of cleaning the containment by pumping a dilute acidsolution into the containment.
 14. A method as claimed in claim 2,wherein the solvent is formulated from derivatives of orange oils and asynthesised mineral oil.
 15. Apparatus as claimed in claim 8, whereinmeans are provided for sequentially restricting the flow throughspecific nozzles as the rotor rotates to provide a desired spreadingpattern.
 16. Apparatus as claimed in claim 9, wherein means are providedfor sequentially restricting the flow through specific nozzles as therotor rotates to provide a desired spreading pattern.
 17. Apparatus asclaimed in claim 8, further comprising valve means between the pump andthe rotor to permit diversion of some of the flow in order to propel theapparatus through the dissolved sludge.
 18. Apparatus as claimed inclaim 9, further comprising valve means between the pump and the rotorto permit diversion of some of the flow in order to propel the apparatusthrough the dissolved sludge.
 19. Apparatus as claimed in claim 10,further comprising valve means between the pump and the rotor to permitdiversion of some of the flow in order to propel the apparatus throughthe dissolved sludge.